A device for withdrawing samples from a suspension flowing through a conduit

ABSTRACT

A device for withdrawing samples of a suspension flowing through a conduit comprises an open-ended cylinder adapted to be inserted through the wall of the conduit. A spindle movable axially through the cylinder carries two spaced pistons as well as a cover plate, the latter being adapted for sealing engagement with the inner end of the cylinder.

ttes atet 1 1 1 1 ,72,143 Enarsson 1 Apr. 10, 1973 [54] DEVICE FOR W1 3,541,860 11/1970 George ..73 421 B SAWLES FROM A SUSPENSIQN 3,115,782 l 2/l963 Echtler, Jr ..73 422 TC FLOWING THROUGH A CONDUH FOREIGN PATENTS OR APPLICATIONS [75] Inventor: E i 5 Same Sweden 6,804,387 9/1969 Netherlands ..73 422 R [73] Assignee: Aktiebolaget Kalle-Regulatorer, Saf- Sweden Primary Examiner-Louis R. Prince 22 Filed: Feb. 16 1971 Assistant ExaminerDaniel M. Yasich Attorney-Mason, Kolehmainen, Rathburn & Wyss [21] Appl.'No.: 115,559

1 ABSTRACT Applicafion Priority Data A device for withdrawing samples of a suspension Mar. 4, 1970 Sweden ..2864/70 flowing t ugh a nduit com rises an open-ended cylinder adapted to be inserted through the wall of the [52] US. Cl. ..73/422 TC, 73/423 R conduit. A spindle movable axially through the [51] Int. Cl. ..G01n 1/10 cylinder carries two spaced pistons as well as a cover [58] Field of Search ..73/422 R, 421 B, plate, the latter being adapted for sealing engagement 73/422 TC, 423 R with the inner end of the cylinder. [56] References Cited 2 Claims, 1 Drawing g e UNITED STATES PATENTS 3,066,539 12/1962 Coker et a1. ..73/423 R 2,811,041 10/1957 Beatty et a1 ..73/422 R nullfllum DEVICE FOR WITHDRAWING SAMPLES FROM A SUSPENSION FLOWING THROUGH A CONDUIT BACKGROUND OF THE INVENTION The invention relates to a device for withdrawing samples from suspensions flowing through conduits, particularly fiber suspensions in the pulp and paper industry. The device is of the type comprising an openended cylinder adapted to be introduced through and secured to the wall of the conduit. A movable spindle extending axially through the cylinder carries two spaced pistons which are slidable along the inner side of the cylinder wall, and the space between said pistons is then less than the length of the cylinder so that at least one piston will always be in sealing contact with the cylinder wall and thus a sampling sluice is formed.

If such a device is used for withdrawing samples from a fiber suspension, it cannot be avoided that fibers become squeezed between the cylinder wall and the inner piston when the latter is drawn back into the cylinder after having been pushed into the pulp conduit. Such squeezed fibers cause a considerable wear which rather soon results in a poorer sealing and this is SUMMARY OF THE INVENTION The invention eliminates this problem by a device which seals effectively. in inoperative position, i.e., when no sample is being withdrawn. For that purpose, the inner end of the spindle carries a cover plate adapted for sealing engagement with the inner end of the cylinder and spaced from the inner piston by a distance which is less than the length of the cylinder, while the distance between the cover plate and the outer piston is greater than the length of the cylinder.

Thus, .the cover plate is normally in sealing contact with the inner end of the cylinder. When the spindle is moved inwards, the pulp caught between the cover plate and the inner piston at the preceding operation is first rinsed out, and when the space between the pistons is then brought into communication with the interior of the conduit it is filled with fresh suspension from a pulp flow which passes transversely to the spindle. The inward movement of the spindle is stopped when the rear or outer piston reaches the inner end of the cylinder. At the withdrawal of the spindle an accurately measured quantity of pulp is enclosed between the pistons, and that quantity is passed through by moving the inner piston outwards to a position just inside of the outer cylinder end. In this position of the inner piston the outward movement is stopped in that the cover plate engages the inner end of the cylinder. An effective seal of the cylinder is obtained by means of the overpressure prevailing in the conduit. The overpressure in the space between the cover plate and the inside of the inner piston now ceases so that the risk of a leakage is eliminated, even if the inner piston should not seal completely. The device is particularly useful for continuous checking operations when equally large samples are to be withdrawn at even intervals to be included in an average sample representative of a determined period of time, such as a work shift.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The sampling device will be described in more detail with reference to the accompanying drawing which shows an axial section through a suitable embodiment.

An open-ended cylinder 2 provided with an annular coupling flange 1 is partly inserted through a short branch socket 3 which projects radially from a considerably thicker conduit 4 the wall of which is only fragmentarily shown. The inner end of the cylinder 2 is located slightly inside of the interior wall of the conduit 4 and the cylinder flange 1 is clamped by bolts 5 between an end flange 6 of the socket 3 and an outer ring'7. The ring 7 carries two bracing rods 8 which extend rearwards from the outer end of the cylinder.

A spindle 9 extending axially through the cylinder 2 carries two spaced pistons 10,11, and a cover plate 12 which latteris secured to the inner spindle end. As appears from a fragmentary section through the rear piston 10, each piston may be composed of a central disk 13, a circumferential sealing ring 14 of Teflon (R), rubber or the like, and two washers 15 each disposed on one side of the sealing ring. The cover 12 may be composed of two disks 16,17 of different size, and a sealing ring 18 of Teflon (R), rubber or the like. The ring 18 is kept clamped between the rim portions of the two disks 16,17, in such a way that it engages the inner end of the cylinder 2. A spacing sleeve 19 is slipped on the spindle 9 between the cover 12 and the foremost piston 11, and another spacing sleeve 20 is placed between the two pistons 10,11. All parts put on the spindle are held together between a nut 20' screwed onto the threaded rear end of the spindle and the head 21 of a screw threaded into the fore end of the spindle. The structure described is simple and cheap, but of course the pistons and the cover may also be designed in many other ways.

The foremost piston 11 is located at such a distance from the cover 12 that it is still in sealing engagement with the cylinder 2 near its outer end when the sealing ring 18 of the cover engages the inner end of the cylinder. On the other hand, the distance between the two pistons is such that both pistons can seal simultaneously against the inside of the cylinder, the foremost piston 11 near the inner end of the cylinder and the rearrnost piston 10 near the outer end of the cylinder.

The spindle 9 may be adapted to be moved by means of a lever or some other mechanism operated manually or mechanically. In the embodiment shown, the rear end of the spindle is connected to a piston rod 22 projecting from a pneumatic cylinder 23 shown only partly. The cylinder 23 is mounted on an annular bracket 24 secured to the two bracing rods 8 mentioned above. Although not shown, the cylinder may, in the known way, be operated by valve mechanisms which may, in turn, be actuated by a time switch that causes the spindle to be reciprocated at determined intervals for withdrawing samples of a suspension flowing through the conduit 4.

The sampling device described operates as follows. Initially, the spindle 9 is in the position shown in the drawing, in which the cover 12 seals the inner end of the cylinder 2. This seal is necessary to avoid an overpressure acting upon the in-side of the foremost piston 11 in the inoperative position of the device. In fact, such a pressure might cause some leakage owing to the tendency of the fibers to be clamped between the cylinder wall and the periphery of the piston 11. When the piston is moved inwardly, the quantity of liquid en closed between the cover 12 and the foremost piston 11 is first fed into the conduit 4 to be carried away by the flow therein. The inward movement of the spindle is continued until the rear piston is in a position near the inner end of the cylinder, so that the space between the pistons 10,11 Is passed by the suspension flowing through the conduit 4. When the spindle is then withdrawn, a quantity of the suspension just passing is trapped between the pistons. When the rear piston 10 leaves the rear end of the cylinder 2, the sample withdrawn is discharged and may be collected in a vessel placed beneath the cylinder. The outward movement of the spindle continues until the initial position shown in the drawing is reached, whereupon the device is ready for next sampling operation.

What I claim is:

1. A device for withdrawing samples of a suspension flowing through a conduit, particularly a fiber suspension, comprising an open-ended cylinder adapted to be introduced through and secured to the wall of the conduit, and a movable spindle extending axially through the cylinder and carrying two spaced pistons slidable in sealing engagement along the inside of the cylinder Wall, the distance between the pistons being less than the length of the cylinder, so that a sampling sluice is formed between said two pistons, characterized in that the inner end of the spindle, (9), carries a cover plate, (12), adapted for sealing engagement with the inner end of the cylinder, (2), and spaced from the foremost piston, (11), by a distance which is less than the length of the cylinder, while the distance between the cover plate, (12), and the rear piston, (10), is greater than the length of the cylinder.

2. A device as claimed in claim 1, characterized in that the cover plate, (12), carries a sealing ring, (18), engaging the inner end of the cylinder, (2). 

1. A device for withdrawing samples of a suspension flowing through a conduit, particularly a fiber suspension, comprising an open-ended cylinder adapted to be introduced through and secured to the wall of the conduit, and a movable spindle extending axially through the cylinder and carrying two spaced pistons slidable in sealing engagement along the inside of the cylinder Wall, the distance between the pistons being less than the length of the cylinder, so that a sampling sluice is formed between said two pistons, characterized in that the inner end of the spindle, (9), carries a cover plate, (12), adapted for sealing engagement with the inner end of the cylinder, (2), and spaced from the foremost piston, (11), by a distance which is less than the length of the cylinder, while the distance between the cover plate, (12), and the rear piston, (10), is greater than the length of the cylinder.
 2. A device as claimed in claim 1, characterized in that the cover plate, (12), carries a sealing ring, (18), engaging the inner end of the cylinder, (2). 